With the decreasing size and increasing performance of electronic devices, multi-layered circuit boards known as “build-up boards” have been used more frequently as electronic circuit boards incorporated in these electronic devices. Each of the build-up boards is produced by alternately laminating circuit boards having surfaces with asperities formed by printed interconnect lines and the like and electrically insulative resin films together in a multi-layered fashion. Laminating apparatuses disclosed in PTL 1 and shown in FIGS. 3 and 4, for example, are used for the manufacture of the build-up boards.
The laminating apparatus shown in FIG. 3 includes workpiece transport units (steps A and A′; indicated by dash-and-dot lines hereinafter), a vacuum laminating device (step B), a flat press device (step C), and a cooling device (step D). Specifically, the workpiece transport units (steps A and A′) intermittently transport sheet-like workpieces W, each of which includes a circuit board and an electrically insulative resin film merely placed on the circuit board, in the direction of the sequence of steps (in a direction from right to left as seen in the figure) while holding the workpieces W between upper and lower transporting films F and F′ (made of PET or the like) unwound from transporting film unwinding machines 10 and 10′. The vacuum laminating device (step B) is disposed in the course of the workpiece transport step (A→A′) in contiguous relation thereto, and includes a vacuum laminating device 50 and the like. The flat press device (step C) makes a workpiece W in which the resin film is brought into intimate contact with the circuit board by the vacuum laminating device into a build-up board (product) having a uniform overall thickness by flattening a surface of the resin film of the workpiece W, and includes a flat press device 60 and the like. The cooling device (step D) cools the build-up board (product) having passed through the flat press device.
In the laminating apparatus shown in FIG. 3, the reference characters 22 and 22′ in the vacuum laminating device 50 designate heating platens each containing a heater and the like, and the reference characters 24 and 24′ designate vacuum frames for forming a reduced-pressure space (vacuum portion) between upper and lower plates 21 and 21′. The reference numeral 51 designates a hydraulic cylinder used for moving the lower plate 21′ upwardly and downwardly; 53 designates a press stand; and 54 designates a support post for supporting the lower plate 21′ movably up and down. The hydraulic cylinder 51 may be an air cylinder.
FIG. 4 is a partial enlarged view of the flat press device 60 in the laminating apparatus shown in FIG. 3. The flat press device 60 includes: a plurality of (only two out of four at four corners are shown in FIGS. 3 and 4) support posts 64 provided upright on a press stand 63; an upper press block 31 fixed to the support posts 64 with fixtures such as bolts and nuts; and a lower press block 31′ fixed to the support posts 64 movably up and down. In the figure, the reference characters 32 and 32′ designate heating platens for heating the workpiece W with the resin film in intimate contact with the circuit board.
In the flat press device 60, the lower press block 31′ is coupled to a hydraulic cylinder 61 via a joint (not shown) or the like, as in the vacuum laminating device 50. Thus, the lower press block 31′ is configured to move upwardly and downwardly as a piston rod of the hydraulic cylinder 61 moves upwardly and downwardly. The hydraulic cylinder 61 may be an air cylinder.
In some cases, a plurality of hydraulic cylinders or air cylinders are used in place of the aforementioned single hydraulic cylinder (designated by the reference numeral 51 or 61) to move the lower press block 31′ of the flat press device 60 and the lower plate 21′ of the vacuum laminating device 50 upwardly and downwardly. For example, as shown in FIG. 5, a known structure for moving the press block 31′ upwardly and downwardly includes a total of five hydraulic cylinders: four (only two out of four are shown) hydraulic cylinders 62 disposed at the four respective corners of the press block 31′ in addition to the hydraulic cylinder 61 disposed at the center of the press block 31′ as seen in plan view.
With regard to the laminating apparatus including the aforementioned steps A to D, the present applicant has already proposed a laminating apparatus in which a vacuum laminating device including upper and lower plates each having a surface provided with an elastic pressing plate made of a heat-resisting rubber is used as the vacuum laminating device of the laminating apparatus to thereby bringing a laminating material (resin film) into tightly intimate contact with and into following engagement with a to-be-laminated material (board) without bubbles between the to-be-laminated material and the laminating material even when the surface of the to-be-laminated material has asperities (interconnect lines) of fine spacing (on the order of 20 μm) or of great depth (not less than 40 μm) (PTL 2).
With regard to the laminating apparatus including the aforementioned steps A to D, the present applicant has also proposed a laminating method in which upper and lower press blocks each having a surface (on press side) provided with a flexible metal plate, with a buffer material therebetween, are used for a flat press device used as the flat press device of the laminating apparatus to thereby provide a laminate having a uniform overall thickness and including a resin film having a surface that is a flat surface excellent in specularity (PTL 3).